You need to select the Group Approval check box for inspection type if you want to use the Lot Walk feature with inspections of the given type.
Features: Lot Walk
To turn on group approval
In the Back Office application, on the Company tab, click Inspection Types, and then click Edit next to inspection type that will be used for creating lot walk inspections.
In the Inspection Type dialog box, select the Group Approval check box, and click OK.
Now you can easily approve multiple inspections of this type created for a particular client.